495 research outputs found
Self-assembly of halogenated cobaltacarborane compounds: Boron-assisted C-H center dot center dot center dot X-B hydrogen bonds?
No full textFull structural characterisation and complete synthetic procedures for three monohalogenated cobaltacarborane compounds closo-[3-Co(5-C5H5)-8-X-1,2-C2B9H10] (X = Cl (1), Br (2), I (3)) and the dibromo derivative closo-[3-Co(5-C5H5)-8,9-Br2-1,2-C2B9H9] (4) are reported. The supramolecular structures of 1, 3, and 4 reveal the existence of intermolecular CHXB interactions. The role of these interactions has been investigated through a CSD search and subsequent analysis of the reported crystalline compounds. The results show that halogens become reasonably good hydrogen-bond acceptors when bonded to boron and, in this respect, are comparable in strength to metal-bound halogens
Polymorphism and phase transformations in cobaltacarborane molecular crystals
No full textThe full study of polymorphism in the cobaltacarborane closo-[3-Co(5-C5H5)-1,2-C2B9H11] ( 1) compound by a combination of X-ray diffraction, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), IR and hot-stage microscopy (HSM) is reported for the first time. The previously reported Form I (orthorhombic Form, noncentrosymmetric space group P21212) crystallizes as dark yellow to orange flat prisms from polar dichloromethane. A new centrosymmetric modification (Form II) that crystallizes from a mixture of polar and non-polar solvents has been found. Form II crystallizes as pleochroic orange blocks in the monoclinic crystal system and space group P21/c. Phase transformation between both polymorphs has been observed by DSC, IR and HSM, showing that the centrosymmetric Form II (kinetic) converts irreversibly to the noncentrosymmetric Form I (thermodynamic)
Linguistic and technical training as a community empowerment tool
No full textThis paper addresses linguistic technical training of members of the community, under a Participatory Action Research approach. We show how it can be a contributing factor to obtain an egalitarian relationship between the speaking community and the external researchers. Also, this training increases the self-sufficiency of the indigenous team, and facilitates their role as agents in research, while being an effective element to facilitate the community’s empowerment process and strengthen their agentive role in linguistic research. The project concerns the Mayangna community of North Eastern Nicaragua. The Mayangna linguists’ team, a team of indigenous linguists, had been established in the mid 1990’s and had been working on the collection of oral history, traditional folktales, and life stories. The team had also received linguistic training. At this point the need to consolidate the linguistic data and its analysis called for an optimization of the handling of the data. The external member of the team provided, then, the technical training for transfer and annotation of the linguistic data collected, which involved the following steps: (a) the use of (video, audio) equipment for (new) data recording, (b) the conversion of the collected data from analog to digital format, (d) the transfer of the linguistic data into ELAN software, and (c) its use for transcription and annotation. The external researcher arranged an ELAN template with the different fields relevant for the actual annotation: original text, sentence, word category, lexical meaning, inflectional information, and Spanish and English translations. The Mayangna team worked with this template in the training sessions, where the whole process (a-d above) was reviewed step-by-step. Once the training sessions were completed, the team of local linguists was able to do the actual recording, transferring and annotation tasks by themselves. These materials will be used in the bilingual educational system, in radio-broadcasting programs and for cultural revival activities. This experience of PAR, involving the equal collaboration of members of the Mayangna community and external researchers, provides an example of how a multi-faceted, continuous linguistic training enhances the process of decision making by the members of the speaking community, since the members of the community, as owners of the data, decide what kinds of elements are to be collected and analyzed and, eventually, what the research will focus on. Besides, this training component results in the empowerment of the language community, as it contributes to their self-sufficiency and autonomy as a linguistic team
Efficient extraction of carrageenans from Chondrus crispus for the green synthesis of gold nanoparticles and formulation of printable hydrogels
No full textThe integral utilization of sustainable resources with versatile, efficient and cleaner processes is encouraged. Hydrothermal treatment with subcritical water is a chemical free, tunable and rapid technology providing enhanced yield compared to conventional extraction and was explored for the benign by design extraction and depolymerization of carrageenan from Chondrus crispus. Up to 90% of the seaweed was solubilized operating under nonisothermal regime during heating up to 200 °C and 75.5% crude carrageenan yield was attained at 140 °C. Crude carrageenan could not be precipitated by ethanol from the extracts produced at 180 °C and higher temperatures, but ultrafiltration (100 kDa) of the extract obtained at 160 °C provided comparable recovery yields and similar rheological features to those of the ethanol precipitated product. Operation at 140 °C was preferred based on the higher recovery yield of the biopolymer and the whole extract was suitable for the green synthesis of polycrystalline decahedral quasi-spherical gold nanoparticles with a mean size distribution of 8.4 nm and Z potential value of −40.2 mV. Alternatively, the crude carrageen fraction was used for the formulation of printable biopolymer based gels with suitable mechanical properties, including a relevant gel strength enhancement (about 10-fold) when compared with conventional procedures
Hypergraph factorization for multi-tissue gene expression imputation
No full textIntegrating gene expression across tissues and cell types is crucial for understanding the coordinated biological mechanisms that drive disease and characterize homoeostasis. However, traditional multi-tissue integration methods either cannot handle uncollected tissues or rely on genotype information, which is often unavailable and subject to privacy concerns. Here we present HYFA (hypergraph factorization), a parameter-efficient graph representation learning approach for joint imputation of multi-tissue and cell-type gene expression. HYFA is genotype agnostic, supports a variable number of collected tissues per individual, and imposes strong inductive biases to leverage the shared regulatory architecture of tissues and genes. In performance comparison on Genotype–Tissue Expression project data, HYFA achieves superior performance over existing methods, especially when multiple reference tissues are available. The HYFA-imputed dataset can be used to identify replicable regulatory genetic variations (expression quantitative trait loci), with substantial gains over the original incomplete dataset. HYFA can accelerate the effective and scalable integration of tissue and cell-type transcriptome biorepositories
Resummed heat kernel and effective action for Yukawa and QED
No full textIn this letter, we prove the existence of resummed expressions for the diagonal of the heat kernel and the effective action of a quantum field which interacts with a scalar or an electromagnetic background. Working in an arbitrary number of spacetime dimensions, we propose an Ansatz beyond the Schwinger–DeWitt proposal, effectively resumming an infinite number of invariants which can be constructed from powers of the background, as well as its first and second derivatives in the Yukawa case. This provides a proof of the recent conjecture that all terms containing the invariants FμνFμν and F ̃μνFμν in the proper-time series expansion of the SQED effective action can be resummed. Possible generalizations and several applications are also discussed—in particular, the existence of an analogue of the Schwinger effect for Yukawa couplings
Asymptotic freedom for
No full textWe analyze the model of a self-interacting scalar field theory in Snyder–de Sitter space. After analytically computing the one-loop beta functions in the small noncommutativity and curvature limit, we solve numerically the corresponding system of differential equations, showing that in this limit the model possesses at least one regime in which the theory is asymptotically free. Moreover, in a given region of the parameter space we also observe a peculiar running of the parameter associated to the curvature, which changes its sign and therefore can be interpreted as a transition from an IR de-Sitter space to and UV anti-de Sitter one
Heavy ions optical potential at finite temperature calculated using a complex effective interaction
No full textHydrothermal extraction and thorough characterization of carrageenans and proteins from Gigartina pistillata
No full textCarrageenan, an interesting biopolymer from red seaweed, possesses a myriad of applications in food, nutraceutical, or pharmaceutical industries. Although its conventional extraction used to be performed with alkaline solvents, water extraction under subcritical conditions is an alternative eco-friendly technique that has gained popularity in recent years. This work evaluates the recovery and characterization of carrageenan and proteins from Gigartina pistillata. The highest number of proteins was identified at the lowest processing tempeartures. Extracted carrageenan exhibits molecular weights greater than 500 kDa and good rheological behaviour, with interest for food applications and for the formulation of hydrogels when mixed with KCl. The carrageenans and carrageenan hydrogels presented interesting properties such as good thermal stability until 170 °C (TGA-DTG) and show characteristic bands of kappa/iota carrageenans in FTIR studies. Greater cell viability than 70% were achieved on NIH/3T3 fibroblast at carrageenan concentrations of 0.05 and 0.025%, whereas carrageenan extracted at 160 °C (concentration of 0.025%) displays a lower inflammatory action than other samples. In this sense, in this work the eco-friendlier extracted carrageenan was thoroughly characterized and its potentiality to be used in the biomedical field was evaluated
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